package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.autoconfigure.cache.CacheProperties;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {

    //注意了 这个工具类方法为什么没有用static修饰 因为有ioc注入 ioc通过new创建bean new是在堆里面 static是优先于对象存在
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(redisData));
    }

    //缓存穿透
    public <R,ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID,R>dbFallback,Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在,直接返回
            return JSONUtil.toBean(json, type);

        }
        //判断命中的是否是空值
        if (json != null) {
            //返回一个错误信息
            return null;

        }
        //4.不存在,根据id查询数据库
//        R r = getById(id);//怎么办?交给调用者! 用函数式编程! 有参有返回值的函数 叫Function
        R r = dbFallback.apply(id);
        //5.不存在,返回错误
        if (r == null) {
            //将控制写入Redis 解决缓存穿透问题
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在,写入redis
        this.set(key,r,time,unit);
        //7.返回
        return r;
    }


    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(String keyPrefix,ID id,Class<R>type,Function<ID,R>dbFallback,Long time, TimeUnit unit) {
        String key = CACHE_SHOP_KEY + id;
        //1.从redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if (StrUtil.isBlank(json)) {
            //3.存在,直接返回
            return null;
        }
        //4.命中 需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1 未过期 直接返回店铺信息
            return r;
        }
        //5.2 已过期需要缓存重建
        //6.缓存重建
        //6.1 获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2 判断获取锁成功
        if (isLock) { //注意:注意获取锁成功应该再次检测redis缓存是否存在,做DoubleCheck如果存在无需重建缓存.
            //6.3 成功,开启独立线程,实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存 查询数据库 存进redis
                    R r1 = dbFallback.apply(id);
                    this.setWithLogicalExpire(key,r1,time,unit);
//                    this.saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }

            });
        }
        //6.4 返回过期的商铺信息
        return r;
    }



    //Redis中的setnx 来模拟互斥锁
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        //不要直接返回flag 它会做一个自动拆箱可能会产生空指针
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }

//    public void saveShop2Redis(Long id, Long expireSeconds) {
//        //1.查询店铺数据
//        Shop shop = getById(id);
//        //2.封装逻辑过期时间
//        RedisData redisData = new RedisData();
//        redisData.setData(shop);
//        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
//        //3.写入Redis
//        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
//    }




}
